In recent years, so-called bioreactors wherein the same biosynthesis as that in the living body is industrially carried out outside the living body have been studied. Among biochemical reactions to be adopted for such devices, there are many cases of using adenosine-5'-triphosphate (hereinafter referred to as ATP) as an energy source. In this case, ATP operates as an energy source for chemical reactions and is converted into adenosine-5'-monophosphate (hereinafter referred to as AMP) or adenosine-5'diphosphate (hereinafter referred to as ADP). Accordingly, if ATP is converted from AMP or ADP at a moderate price, the bioreactor becomes more advantageous economically because it is not necessary to waste expensive ATP. However, hitherto, ATP has been obtained by extracting it from animal tissues or by a batch process such as a fermentation process utilizing microorganisms. Consequently, ATP is inevitably very expensive, because the production efficiency is inferior or purity is low and a complicated purifying step is required because of culture residues as described in R. S. Langer, B. K. Hamilton, C. R. Gardner, M. C. Archer and C. K. Colton, AlChE J., 22, 1079 (1976), and Japanese Patent Application (OPI) Nos. 136591/78 and 24036/80 ( the term "OPI" as used herein refers to a "published unexamined Japanese patent application "), etc. This fact is an obstacle with respect to the practical application of bioreactors. Accordingly, there has been a strong desire to develop a new technique for converting into ATP having a high purity at a moderate price.
In view of such requirement, attempts have been made at utilizing ATP conversion enzymes. For example, Langer et al. reported a process for converting AMP into ATP by means of adenylate kinase in rabbit muscles and acetate kinase in Escherichia coli in R. S. Langer, B. K. Hamilton, C. R. Gardner, M. C. Archer and C. K. Colton, AlChE J., 22, 1079 (1976) and U.S. Pat. No. 4,164,444. Further, it has been reported to convert adenosine into ATP using adenosine kinase in addition to the above-described two kinds of conversion enzyme (R. L. Baughn, O. Adalsteinsson and G. M. Whitesides, J. Am. Chem. Soc., 100, 304 (1978)). Further, reports have been written with respect to the use of immobilized enzymes, but the stability of such with the passage of time is remarkably inferior (G. M. Whitesides, A. Chmurny, P. Garrett, A. Lamotte and C. K. Colton, Enzyme Eng., 2, 217 (1974)). The process of using such enzymes is not suitable industrially, because it is not a process for continuously converting into ATP efficiently over a long period of time by a systematic method. Accordingly, there has been a need to develop an apparatus for constantly, effectively and stably converting into ATP over a long period of time.